The term "superconductivity" is applied to the phenomenon of immeasurably low electrical resistance exhibited by materials. Until recently superconductivity had been reproducibly demonstrated only at temperatures near absolute zero. As a material capable of exhibiting superconductivity is cooled, a temperature is reached at which resistivity decreases (conductivity increases) markedly as a function of further decrease in temperature. This is referred to as the superconducting transition temperature or, in the context of superconductivity investigations, simply as the critical temperature (T.sub.c). T.sub.c provides a conveniently identified and generally accepted reference point for marking the onset of superconductivity and providing temperature rankings of superconductivity in differing materials. The highest temperature at which superconductivity (i.e., zero resistance) can be measured in a material is referred to as T.sub.O.
A. H. Hamdi, J. V. Mantese, A. L. Micheli, R. C. O. Laugal, and D. F. Dungan, "Formation of thin-film High T.sub.c Superconductors by Metalorganic Deposition", Appl. Phys. Lett., 51 (25), Dec. 27, 1987, reports the formation of 500 nm thin films of YBa.sub.2 Cu.sub.4 O.sub.z (z undetermined) on {100} SrTiO.sub.3. A superconducting onset temperature (T.sub.c) of 90.degree. K. was measured with T.sub.o occurring at 37.degree. K. When the process was repeated with YBa.sub.2 Cu.sub.3 O.sub.z, both crystal sizes and T.sub.o where lower.